Method of shaving gears



Dec. 1, 1953 w. s. PRAEG METHOD OF SHAVING GEARS Filed Jan. 13, 1949llll III II IIIHII llllllill INVENTOR.

WALTE s. PRAEG BYW z T 75k ATTORNE s Patented Dec. 1, 1953 l..-

METHOD OF SHAVING GEARS Walter S. Praeg, Detroit, Mich assignor toNational Breach and Machine Company, De troit, Mich., a corporation ofMichigan Application January 13, 1949, Serial No. 70,678

' The present invention relates to a method of shaving gears.

It is an object of the presentinvention to pro- 'vide a method ofshaving-gears which ischaracterized by the independent rotation in timedrelation of a gear and e, gear-like finishing tool with their axescrossed, the tool having cutting edges only atthe ends of its teeth, inconjunction with relative traverse between the gear and tool in adirection occupying a plane parallel to the axes of both gear andcutter, in which the gear and cutter are positioned such that clearanceexists in back of the cutting edges of the cutter teeth; I 1

Other objects and features of the invention will become apparent .as thedescription proceeds, especially When taken in conjunction with theaccompanying drawings, where:

Figure 1 is a perspective view of an apparatus employed in the finishingof gears by the'present method;

Figure 2 is a side elevation of a gear and cutter illustrating theirrelationship during the cutting operation;

7 Figure 3 is a side elevation of a gear and somewhat difierent cutterillustrating theirrelationship during the cutting'operation.

The present invention is characterized by the use of a cutting tool inthe form of a circular gear, the teeth of the tool having cutting edgesat the ends thereof. The cutter is designed to mesh and be conjugatewith a circular gear to be finished when the axes of the gear and toolare crossed or angularly disposed with respect to each other. The angleat which the axes of the gear and tool are crossed is preferably lessthan30 and excellent results are obtained When the angle of crossed axesis about to 20. However, in the present method the angle may exceed 30.

It is desirable to provide cutting clearance in back of the cuttingedges on the cutter. may be accomplished in several ways. In the firstplace the teeth of the cutter may be relieved so that the tool resemblesa shaper cutter. Alternatively the cutter may have teeth which are notrelieved and which are uniform from end to end. In this case cuttingclearance may be provided by introducing an additional inclinationbetween the gear and cutter so as to provide cutting clearance. Finally,a cutter having unrelieved teeth may be positioned with respect to agear such that the commonmormal to the axis of the gear and tool islocated a substantial distance ahead of the cutting edges on the cutterteeth. This also introduces effective cutting clearance during theoperation.

This

4 Claims. (Cl. 90,-1.6)

Referring now to Figure 1 there is illustrated an apparatus for carryingout the present method of gear finishing. This apparatus comprises aframe ill havinga column ii and a bed i2 constituting ways on which acarriage as is mounted for traversing movement. Mounted for verticaladjustment on the column ii is a slide l5 which carries a gearsupporting spindle is on which the worl; gear W is mounted. Carried bythe cutter carriage is asupport 243 carrying cutter spindle 2! extendingat an angle to spindle l6 and on which the cutter C is mounted.Conventional .means such as arcuate ways 25 are provided for angularadjustment of support 29 about a vertical axis. horizontal and thecutteris of the relieved tooth type similar to a conventional gearshaper cutter. Means are provided for independently rotating thespindles it and 2i in accurately timed relation. This means isillustrated as comprising an electric motor E5 connected by a belt 26 toa puliey 21 mounted on a cross shaft 28. At the end of the shaft 28 is abevel gear 2% meshing with a bevel gear as mounted on a shaft 3i whichextends longitudinally of the machine. 3i carries a bevel gear 32 whichmeshes with a bevel gear 33 on a vertical shaft 3 3, the upper end ofwhich carries a bevel gear The support 29 is mounted for angularadjustment about a vertical axis concentric with the axis of thevertical shaft 34. 'Mounted on the support Bil is a bevel gear 33 whichis adapted to mesh with the bevel gear 35 in all positions of angularadjustment of the support 36. Bevel gear ii? is carried by a shaft tilon which is also secured a driving gear it which meshes with gear i2keyed or otherwise secured to the cutter spindle 2 i.

The longitudinally extending shaft 3i at its opposite end carries a gear56 meshing with a gear 5| connected to a differential housing 52.Located within the housing 52 is a planetary gear set indicatedgenerally at 53, one of which is driven froma shaft 54 which carries aworm gear 55. The worm gear 55 is driven from a Worm 55 carried by ashaft 5! which also carries a gearss. The gear 58 in turn is driven bygear 59 carried by shaft 5% which also carries a bevel gear 5i. Thebevel gear 6! meshes with a bevel gear 62 mounted on a screw shaft tithshaft 63 having a threaded portion engaging a feed nut indicatedgenerally at 64. The shaft 63 is rotated from the prime sourceof powerand specifically from the shaft 3! through ears c5 and E6, the gear 6-6-In this case both the spindles is and 2! are r The shaft curately timedrotation independently of traverse of the carriage 13, this beingaccomplished through the diiferential previously referred to.

The differential drives a shaft which in turn drives a worm H throughthe medium of gears l2, l3, l4 and bevel gears and H5. The worm H mesheswith the worm wheel 18 keyed or otherwise secured to the work spindlel6.

Carrying out the operation the cutter is angularly adjusted to theproper position to mesh with the teeth of the work gear W and is locatedso that the common normal to the axis of the gear and cutter is at oroutside the face of the gear at which the out is to be initiated as"illustrated in Figure 2. At the same time the common nor-- mal to theaxis or" the gear andcutter is located substantially in the plane of thecutting teeth of the cutter. The gear and cutter are rotated atrelatively high speed so as to obtain a peripheral surface speed of thegear and cutter on the order of several hundred feet a minute. Traverseeffected through the feed screw 63 and the feed'nut Ed is relativelyslow on the order of a few thousandths of an inch per revolution of theworl: gear. The teeth of the gear W are finished in a single pass.Preferably means are provided for eiiecting a relieving movement betweenthe cutter and the gear upon completion of the stroke followed by arapid return of the carriage I3 to initial position.

Instead oi employing a relieved cutter of the shaper cutter type, itwill be appreciated that equivalent results may be obtained if a cutterhaving unrelieved teeth is employed and if the cutter spindle isadditionally inclined soas to provide cutting clearance. Thisarrangement is illustrated. in Figure 3 in which the cutter spindle isillustrated as inclined to the horizontal through an angle indicated atA so as to provide cutting clearance. this may be accomplished in themachine illustrated in Figure 1 by the simple expedient of appropriatelyinclining the adjustable support 20. Specifically this would beaccomplished by raising the right hand end of the support 20 as seendicated by the angle A if it is mounted so that the cutting ends of theteeth are spaced a substantial distance away from the common normal tothe axis of the gear and cutter. chine illustrated in Figure 1 thiswould call for setting the cutter C to the left on the cutter spindle2!, which in turn would result in the out being taken somewhat to theleft of the bottom portion of the work gear W.

The drawings and the foregoing specification constitute a description ofthe improved method of shaving gears in such full, clear, concise andexact terms as to enable any person skilled in the art to practice theinvention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. The method of finishing a gear of cylindrical form which comprisesmeshing it in tight mesh with a gear-like cutter of cylindrical formhaving teeth provided with cutting edges at the ends thereof, with theaxes of said gear and cutter crossed to produce a substantial relativemotion As will be readily apparent In the ma-' iii) between the gear andcutter endwise of the teeth thereof, said cutter teeth being uniformfrom end to end, said cutter being additionally inclined with respect tosaid gear so as to introduce cutting clearance in back of the cuttingedges, rotating said gear and cutter independently in accuratelytiinedrelation at cutting speeds, and efi'ectin'g a slow relative traversebetween the gear and cutter in a direction parallel to the axis oi thegear to distribute the finishing out of the cutter from end to end ofthe gear teeth.

2. The method of finishing a gear of cylindrical form which comprisesmeshing the gear in tight mesh with a gear-like cylindrical cutter withthe axes of the gear and cutter crossed at an angle of less than 30, thecorresponding ends of the teeth of the cutter forming cutting edges, theteeth of said cutter being unreiieved in back of said cutting edges, thecutter being located with the common normal to the axes of the gear andtool spaced outwardly from the plane of its side containing the cuttingedges, rotating said gear and cutter independently at cutting speeds inaccurately timed relation, and effecting a slow relative traversebetween the gear and cutter in the direction of the axis of the gear.

3. A. method of shaving a gear employing a gear-like tool having teethof uniform cross section and provided with cutting edges only at theends of its teeth, which comprises tightly meshing the gear and cutterwith their axes crossed at an angle of less than 30 degrees, and both ofsaid axes being parallel to a reference plane, the common normal to theaxes being located outwardly beyond the side of the tool at which theteeth are provided with cutting edges, driving the gear and toolindependently in accurately timed relation at cutting speeds, andeffecting relative traverse at feeding speeds between the gear and toolto extend the cut from end to end of the gear teeth.

i. The method of finishing a gear of cylindrical form which comprisesmeshing the gear in tight mesh with a gear-like cylindrical cutter withthe axes of the gear and cutter crossed at an angle of less than 30degrees, the corresponding ends of the teeth of the cutter formingcutting edges, the teeth of said cutter being unrelieved in back of saidcutting edges, the cutter being positioned to provide clearance directlyin backcf said cutting edges, rotating said gear and cutterindependently at cutting speeds in accurately'timed relation, andeffecting a slow relative traverse between the gear and cutter in thedirection of the axis of the gear.

WALTER S. PRAEG.

References Cited in the his of this patent UNITED STATES PATENTS NumberName Date 2,157,981 Drummond May 9, 1939 2,282,193 Lambrix May 5, 19422,318,179 Mentley May 4, 1943 2,372,444? Mehtley Mai. 27, 1945 2,434,432Austin Oct. 11, 194.9 2,499,1'6? Sanborn Feb. 28, 1950 FOREIGN PATENTSNumber Country Date 698,881 Germany Nov. 19, 1940

